1. Field of the Invention
The present invention is directed to a valve for regulating a gas flow of the type having a valve body which is movable against a valve seat to regulate a degree of opening of the valve, thereby regulating the gas flow through the valve.
2. Description of the Prior Art
Valves for regulating gases are available in many different versions, all with varying performance (e.g. in terms of dynamic regulatory range and accuracy), operating reliability and operating costs.
The aforementioned properties are important in certain applications, such as valves in ventilators for respiratory care. Such valves must have a wide dynamic range and high accuracy for correct ventilation of all patient categories. Their operating reliability must be great and operating costs low.
One such valve is described in U.S. Pat. No. 5,265,594. This known valve is an electromagnetic, servo-controlled membrane valve.
Although this known valve displays excellent performance and operating reliability, it is also relatively complex and energy demanding.
An object of the present invention is to provide a valve with a design, offering basically the same high performance and high operating reliability as the aforementioned conventional valve, but which is less complex and employs a less complicated regulatory system with lower operating costs.
The above object is achieved in accordance with the principles of the present invention in a valve for regulating a gas flow having a valve body movable relative to a valve seat, wherein the valve body is constrained so as to move only substantially axially against the valve seat, and wherein a stepper motor is used to actuate axial movement of the valve body relative to the valve seat, with the stepper motor and the valve body having a non-linear engagement so that the valve body performs continuous, non-linear, axial movements relative to the valve seat.
Regulation is facilitated by the non-linear connection of the valve body to a stepper motor. The valve body""s continuous non-linear movement against the valve seat results in a large dynamic range for the stepper motor within a small regulatory area of movement, and accuracy at small flows is retained. The stepper motor is also powerful and able to cope with very large counter-pressures without valve leakage.
xe2x80x9cContinuous non-linear movementxe2x80x9d as used herein means movement of a type produced by rotation of a non-linear screw-thread, such as a screw-thread wherein the respective flights have different spacings or inclinations relative to one another, as opposed to a conventional screw-thread with step-wise uniformly spaced and identically inclined flights.